1. Field of the Invention
The present invention is directed generally to a control device and more particularly to a control device for a motor vehicle including a pressure tight housing surrounding a pressure sensor and a printed circuit board.
2. DESCRIPTION OF THE RELATED ART
A control device is disclosed, for example, in German Patent No. 30 13 760. As shown therein, the pressure sensor has a pressure pick-up element which is secured in or on a printed circuit board. The pressure pick-up element is covered by a connecting funnel on the circuit board and must be sealed from the environment. The printed circuit board and the parts thereon can be damaged by this connection. Moreover, the connecting funnel must project out of the housing of the control mechanism for connection to a pressure hose. However, vibrations which occur due to the relatively rough operation of an internal combustion motor are transmitted from the housing directly to the pressure sensitive circuit board.
A pressure sensor which includes a pressure pick-up element and a sealed connecting funnel inverted thereover also requires a great deal of space on a printed circuit board. The printed circuit board and the housing in which it is mounted must accordingly be relatively large, which runs contrary to the increasing tendency for smaller and more compact elements.
A further problem in the prior art is that the chacteristic, or response curve, of the pressure sensor requires equalization. To this end, access must be provided to the electrical terminals of the pressure sensor in the completely assembled pressure sensor to be able to connect or adjust an appropriate equilization means. At the same time, however, the equilization elements which are already on the printed circuit board must also be accessible so that the pressure characteristic can be adjusted by adjustment of the equilization elements.
A solution to this problem is to provide the electrical terminals of the pressure sensor conducted to the outside of the housing. During production, the equilization means is capable of being easily connected to the external connections instead of being connected to the sensitive printed circuit board. This also facilitates access to the equilization elements on the printed circuit board within the housing However, connecting the terminals to the outside of the housing adds an additional cost factor since outside terminals must be incased after the equilization adjustment to avoid corrosion.